But then you start chasing your tail. The weight of landing gear and aerodynamic controls, requires more propellant mass, which requires larger tanks, which requires more thermal protection mass, which raises gross weight, which means more mass for landing gear and structure. Which leads to so on and so forth. So you either wind up with a monster like the STS or an impractically small payload (like the X-37B most likely).

That already appears to be taken in to account with the quoted reduction in payload mass from 10 to 6T. 4T sound about right for heat shielding, landing gear and fuel (given it doesn't go as high as the current first stage)

I have to assume that at some point Musk and his team have worked all this stuff out, rather than just making up some figures.

The cylindrical body is also more volume efficient than a cone. It's closer to a sphere (the most effecient shape) which means less material to enclose the same volume, which lowers the overall mass. I like these designs, and the corperate concepts behind them. The more the private sector helps with supplying the tools of spaceflight, the lower the price can get compared to doing it all in house by NASA.

I don't really understand the push to go back to the moon, though. Unless you're planning to take mining equipment, there's really rather little to be gained there, other than PR.

_________________"You can't have everything, where would you put it?" -Steven Wright.

That is the intent. To get the first human "foothold" out of LEO, to learn how to live in situ while still being able to get help from back home. Besides there are useful things you can do on the Moon. Astronomy, other science, and industrial process that are hard/impossible to do here (free hard vacuum! just open a window).

That is the intent. To get the first human "foothold" out of LEO, to learn how to live in situ while still being able to get help from back home. Besides there are useful things you can do on the Moon. Astronomy, other science, and industrial process that are hard/impossible to do here (free hard vacuum! just open a window).

When you open the window, probably best to ensure you have a fly screen.

That is the intent. To get the first human "foothold" out of LEO, to learn how to live in situ while still being able to get help from back home. Besides there are useful things you can do on the Moon. Astronomy, other science, and industrial process that are hard/impossible to do here (free hard vacuum! just open a window).

I understand all that, but that's not what we're planning. If we were taking mining equipment, the trip could eventually pay for it'self. The current designs have no room for that, because they're budget tickets, (SWAL doesn't fly there.) Right now all we got planned is another flag planter, and photo-op mission, which we have very little to learn from.

Astronomy from the lunar surface isn't a great plan. With the month long "Day" you'll have access to one sky, for most of a fortnight, then be in sunshine the other half of the time. If we wanted to do an extremely long exposure for a deep feild, it might be nice, but that would pay off once, at increadible expense, and we currently have nothing likeat planned. Orbital Telescopes, like the ones we already have, have access to most of the sky all the time.

The moon isn't a Hard Vaccuum. That's about as impossible as producing absolute zero Kelvin, or perpetual motion. We can get about as close in GEO, with a lot better access. There are raw materials in the regolith, however, which could be shipped to LEO cheaper than from Earth, but first we'd need the industrial processes.

I'm not saying we don't need the moon. I'm saying if we're going to use it, we need to use it, not spend trillions of dollars on another commercial.

_________________"You can't have everything, where would you put it?" -Steven Wright.

Dude, lunar "day" isn't the same as "day". You don't have an atmosphere - there is no glow, you can clearly see all of the stars. As long as the telescope doesn't point at the sun then everything is fine. Also, if you want to do really crazy cosmology research having a telescope inside of a permanently shaded crater would be pretty ideal.

Right now all we got planned is another flag planter, and photo-op mission, which we have very little to learn from.

Not really, the first missions are to establish the "base camp", learn how to live and work there and lay the infrastructure for expanding, to include industrial and commercial exploitation. It is/was/will be a persistent presence, as long as the money and politicians stick with it.

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Astronomy from the lunar surface isn't a great plan.

In addition the TerraMrs' comment, the far side of the Moon will make an excellent radio telescope position because it blocks the "noise" from Earth.

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The moon isn't a Hard Vaccuum.

Its hard vacuum from an industrial perspective, and for about 99% of scientific need. Creating a similar "near-vacuum" on Earth is both energy intensive and expensive.

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I'm not saying we don't need the moon. I'm saying if we're going to use it, we need to use it, not spend trillions of dollars on another commercial.

Not really, the first missions are to establish the "base camp", learn how to live and work there and lay the infrastructure for expanding, to include industrial and commercial exploitation. It is/was/will be a persistent presence, as long as the money and politicians stick with it.

That's the proposal, which hasn't been funded yet. By the tim it is, under the current economy, we might be lucky to get the photo op.

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In addition the TerraMrs' comment, the far side of the Moon will make an excellent radio telescope position because it blocks the "noise" from Earth.

Good idea, now, how? You know what a radio telescope looks like, any idea what the assmbly process is like? That's shipping it from Earth, unless we get materials production on the moon, which might make it feasable. I'd rather put a sattelite at the L2 point, opposite the Earth, because then it doesn't have to be designed to land, and be re-assembled.

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Its hard vacuum from an industrial perspective, and for about 99% of scientific need. Creating a similar "near-vacuum" on Earth is both energy intensive and expensive.

That's called a near-vaccuum, a hard one is something else entirely. We can get the same thing in orbit, without Gravity (even 1/6) which also makes these techniques you're talking about more possible. For instance, if you wanted to coat the inside of a module with diamond via evacuated methane deposition, you could get the entire surface, instead of just the bottom. A centerfuge could also simulate gravity, on demand, at whatever intensity you wanted.

If we're going to do this, it needs to be well thought out, and executed.

_________________"You can't have everything, where would you put it?" -Steven Wright.

All right, at what point are you arguing just to argue? No, it doesn't Have to be a dish, but that's the most efficient design, because it focuses a large collection area on a relatively small antenna. It's also directional, so you can tell which direction the signals are comming from. I guess it would be cheaper to rig up some coat-hanger rabbit ears with a little tin foil, but what good would that do?

Yes, there are other designs, but regardless of configuration, you still have to get it there, land it in one peice, and set it up. On the far side of the moon, I might add, which means out of radio contact with the rest of humanity. Or, we could save a lot of trouble, and orbit it at the libration point like I suggested. It would still be limited when the moon is pointed at the sun (You think Earth puts out interference?) but at least it wouldn't have half the sky blocked by the moon.

_________________"You can't have everything, where would you put it?" -Steven Wright.

No, it doesn't Have to be a dish, but that's the most efficient design, because it focuses a large collection area on a relatively small antenna.

Craters make very good short wave antenna dishes. Place a few around the Moon and scatter a bunch of long wave arrays and you have created a telescope with the angular resolution of 3,400 kms (the diameter of the Moon) with interferometry.

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Yes, there are other designs, but regardless of configuration, you still have to get it there, land it in one peice, and set it up. On the far side of the moon, I might add, which means out of radio contact with the rest of humanity.

Repeaters, relay satellites. The antennas can be self deploying and orienting. Here is the LWA in New Mexico:

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Or, we could save a lot of trouble, and orbit it at the libration point like I suggested.

You still have to maintain station keeping and orientation. And it would be tiny and short lived compared to what you can set up on the Moon. An orbiting one would also be nice though for pointing at "snap" targets of interest.

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It would still be limited when the moon is pointed at the sun (You think Earth puts out interference?) but at least it wouldn't have half the sky blocked by the moon.

Nope. A radio telescope works just fine in the "daytime". The moon rotates.

Craters make very good short wave antenna dishes. Place a few around the Moon and scatter a bunch of long wave arrays and you have created a telescope with the angular resolution of 3,400 kms (the diameter of the Moon) with interferometry. The problem with that is, the craters are pointed up, which means in opposite directions clear across the surface of the moon. Remember, dishes are directional, so with the seperation you suggest, 1) they can't point at the same target, for interferometry, and 2) only one can be shielded from interference from the Earth.

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Repeaters, relay satellites. The antennas can be self deploying and orienting. Here is the LWA in New Mexico:

The relay system would work better for a sattelite than a fixed surface instilation. Oh, and I've been there.

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You still have to maintain station keeping and orientation. And it would be tiny and short lived compared to what you can set up on the Moon.

Stationkeeping can be maintained by current technology, we already have space telescopes, they handle it just fine. We don't have ANY lunar surface instilations, nor resources, so those would have to be developed.

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A radio telescope works just fine in the "daytime". The moon rotates.

An Earth based dish is protected by the Magnetosphere. The lunar surface is not. Neither is a sattelite over it, so it would have to be shielded during the "Day", especially in the event of solar storms. Either design would be basically blind for about 2 weeks. Yes, it rotates, 1nce per month, but that's a factor whether it's on the surface, or in orbit. My point is, an orbiting one is easier to do (Therefore affordable), and can move with it's station keeping thrusters to point wherever it wants. A fixed instilation would have to wait, as long as a month for an imaging window.

_________________"You can't have everything, where would you put it?" -Steven Wright.

About 12 minutes in, one of the panel members made an interesting comparison between what is considered to be a profitable mine on Earth and what the LCROSS data suggests is available near surface in some shadowed craters on the Moon. He said a mine on Earth might be profitable if you can make in the range of $150 per ton of material excavated. But judging from the LCROSS data, the minerals available in shadowed craters might value in the range of $1,000,000 per ton of excavated material. This might be sufficient justification for some mining companies to pay for a low cost exploratory lander mission. For instance the Dnepr rocket can lift 550 kg to TLI at a cost of $10 to $13 million. This might be sufficient mass for a lander with a descent rocket with just simple instruments such as a APXS and infrared spectrometers and radio transmission capability.

The estimates from the value of minerals in shadowed craters on the Moon stems from the LCROSS mission results that showed precious metals within the impacted crater such as gold and silver:

If the actual amount is anywhere close to this amount then this would provide mining opportunities for gold even when you take into account the much greater transportation costs for getting it from the Moon. What HAS to be done, like yesterday, is to send lander missions to confirm those startling amounts indicated by the LCROSS mission. The LCROSS readings for gold are only upper bounds. It needs to be determined if the actual amounts are really close to that. If so, then this is a real game changer. People have been asking what is the real "killer app" for space travel? IF the LCROSS results are true then you have it right there, lunar mining. Even more, this is in fact a killer app for beyond Earth orbit space travel as well!

Today's media alert says the new company "will overlay two critical sectors — space exploration and natural resources — to add trillions of dollars to the global GDP. This innovative start-up will create a new industry and a new definition of 'natural resources.'" "That sounds like asteroid mining," Christopher Mims writes on MIT Technology Review's "Mims' Bits" blog. "Because what else is there in space that we need here on earth? Certainly not a livable climate or a replacement for our dwindling supplies of oil." Parabolic Arc's Doug Messier, meanwhile, writes that the venture will be an "extraterrestrial mining company." Diamandis has said on more than one occasion that he's intrigued by the idea of digging into asteroids, for materials ranging from water (for fuel as well as for astronauts) to precious metals such as platinum. The Verge points to a TED talk in 2005 where Diamandis discusses his dream, while Forbes magazine has brought up the subject with him more than once in the past few months.

In regards to the reason for this endeavor, several studies have shown many of the important metals for high technology such as platinum at present global growth rates, especially in the emerging economies such as China, will be depleted within decades:

If these reports are true, and there is some uncertainty in the estimates, then such asteroid mining missions, might turn out to be not merely amusing topics of discussion, but actual necessities.

Bob Clark

_________________Single-stage-to-orbit was already shown possible 50 years ago with the Titan II first stage. Contrary to popular belief, SSTO's in fact are actually easy. Just use the most efficient engines and stages at the same time, and the result will automatically be SSTO.Blog: http://exoscientist.blogspot.com